STUDY OF THE X70 PIPELINE STEEL CORRODING IN 3.0wt% NaCl SOLUTION USING ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY TECHNIQUE

The corrosion process of the X70 pipeline steel in 3.0wt% NaCl solution were studied using polarization method, and the chronological characteristics during the entire polarization plot were investigated in detail using EIS technique. In the active region of X70 steel, such as 20mV potential bias applied on open circuit potential (OCP), the impedance spectra was comprised of three parts: a high-frequency capacitive loop, a middle-frequency capacitive loop and a low-frequency inductive component. When positive polarization potential increased, the capacitive loops at high and middle frequency range merged, and the inductive component at low frequency shrunk. At high positive polarization potential bias (500-800mV vs. OCP), the high-frequency capacitive loop and the low-frequency inductive loop exhibited as disheveled points due to the synergism of the inhomogeneity of the corroding material and the localized corrosion. The results were fitted utilizing the equivalent circuits to simulate the impedance spectra and to interpret the electrochemical features shown during the experiments.

ELECTROCHEMICAL NOISE FEATURES OF PURE ALUMINUM DURING PITTING CORROSION IN NEUTRAL NaCl SOLUTION

Spontaneous electrochemical noise (EN) can be a rich source of information concerning the processes simultaneously occurring at a corroding interface. Potential noise fluctuations during the free corrosion of pure aluminum in different concentration of neutral sodium chloride solution are investigated, and the breakdown and restoration of passive metal's film are studied using potentiodynamic scanning (PDS) measurements and electrochemical impedance spectroscopy (EIS) technique. Two capacitance loops are observed in the Nyquist plots in two kinds of concentration, and the corrosion process is under activation control at first, then become diffusion control within the oxide film and corrosion products of (Al(OH)p-mCl-m) accumulated on the surface of the corroding electrode. It is suggested that the pitting corrosion is much easier to occur for pure aluminum in 7.0wt% than in 2.0wt% NaCl solution, and the high concentration of chloride ion in solution inhibits the repassivation of a metastable pit. The corrosion rate deterministic step does not involve Cl-.

ELECTROCHEMICAL FEATURES DURING PITTING CORROSION OF LY12 ALUMINUM ALLOY IN DIFFERENT NEUTRAL SOLUTIONS

The electrochemical features of commercial airfrarne material, Al alloy LY12, in 0.349mol/L neutral sodium chloride (NaCl) and sodium sulfate (NazSO^) solutions were investigated by electrochemical impedance spectroscopy (EIS) and potentiody-namic polarization techniques. The microstructure of the as-tested samples was studied by scanning electron microscopy. The results show that the Nyquist plots of LY12 at different immersion time displayed different features, indicating that the Cl- ions elevate the corrosion rate and inhibit the repassivation of a metastable pit. It also shows that the corrosion product of LY12 formed in SO42- solution isn't easy to dissolve, and it will cover the surface of working electrode in the electrolyte. SEM images indicate that the corrosion apparent area and pit number of LY12 in NaCl solution are greater than that in Na2SO4 solution.

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DURING CORROSION PROCESS OF 8090 Al-Li ALLOY IN EXCO SOLUTION

The corrosion behavior and electrochemical impedance spectroscopy (EIS) features of 8090 Al-Li alloys in EXCO solution were investigated, and the EIS was simulated using an equivalent circuit. At the beginning of immersion in EXCO solution, the EIS is comprised by a depressed capacitive arc at high-mediate frequency and an inductive arc at low frequency, and the inductive component decreases and disappears with im- mersion time. Once exfoliation or severe pitting corrosion is produced, two capacitive arcs appear in the EIS. These two capacitive arcs are originated from the two parts of the corroded alloy surface, the original flat alloy surface and the new inter-face exposed to the aggressive EXCO solution due to the exfoliation or pitting corrosion. Some corrosion development features of 8090 Al-Li alloys in EXCO solution can be obtained through simulated EIS information.

INFLUENCE OF SO_4^(2-) AND Cl-ON THE CORROSION BEHAVIOR OF COPPER TUBE IN AIR-CONDITIONING SYSTEM

The influence of chloride or sulphur dioxide on the corrosion behavior of copper tube in the air-conditioning system was studied using scanning electron microscope (SEM), energy dispersion spectrometer (EDS) and cyclic polarization techniques. The results showed that the corrosion of copper tube are mainly caused by the SO42- and Cl- ions in the circulating water, and the former is mainly responsible for the general corrosion of the copper tube whilst the latter for the pitting corrosion. The different influences of SG42- and Cl- ions on the corrosion type of copper tube may be attributed to that the radius of SO42- ion is much larger than that of Cl- ion. Meanwhile the results also indicated that SO42- inhibits the pitting corrosion caused by Cl- and Cl- inhibits the general corrosion initiated by SO42- due to their competitive adsorption on the copper matrix.

ELECTROCHEMICAL NOISE ANALYSIS OF THE INFLUENCE OF THE Zn^(2+)IONS CONCENTRATION ON ZINC ELECTROPLATING

The influence of the concentration of Zn2+ ions on zinc electroplating process was investigated by means of electrochemical noise (EN) and cyclic voltammetry methods in conjunction with the scanning electron microscopy (SEM) technique. It was found that the EN generated during the electroplating of dentritic or large polymeric zinc deposit has large potential oscillation amplitude and positive potential drift while the compact zinc deposit possesses small noise amplitude and little potential drift. With the change of rate determining step from diffusion-control through mixed-control to activation-control, the maximum relative energy obtained from wavelet analysis defined from the region with larger scales to those with smaller scales, and the EDP (relative energy distribution plot) can be us, as 'fingerprints' of EN to characterize the electroplating process and the deposit structure. The results also showed that electrochemical noise technique can give more information about the electrodeposit structure than other normal electrochemical measurements, such as linear potential sweep method and cyclic voltammetry technique.

EIS ANALYSIS ON THE ANODIC PROCESS OF ZINC IN AN ALKALINE SOLUTION

yThe EIS on theanodic process of pure Zn in an alkaline solution wereperformed and fitted using the expression of Faradic admittance,based on which the mechanism of the process was proposed.The results showed that besides electrode potential E the electrochemical reaction rate was affected by the adsorption of Zn(OH)ads on the electrode surface and the diffusion of in the electrolyte in active region,and only by the covering of passivation layer on the electrode surface in both transitive and passivation regions.The equivalent circuit sapplied in these various circumstances were proposed and the variation of some parameters and state variables was also discussed.

STUDY THE INFLUENCE OF H_(3)BO_(3)ON THE ZINC ELECTROPLATING USING ELECTROCHEMICAL NOISE TECHNIQUE

The influence of H3BO3 on the zinc electroplating was studied using electrochemical noise technique, cyclic voltammetry and steady-state polarization method. The results showed that, under the experimental conditions, the deposition of zinc followed the mechanism of two-dimensional nucleation and subsequent grain growth. The addition of H3BO3 into the electroplating solution prominently changes the nucleation and growth kinetics of zinc deposits, which is directly related to the features of electrocrystallization noise and the corresponding structure of the electrodeposits. The results also shown that the electrochemical noise (EN) technique can give more information about the electrodeposits structure and electroplating mechanism than other normal electrochemical measurements can give, such as steady-state polarization method and cyclic voltammetry technique.

Amplitude analysis of the decays D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)

Using e^(+)e^(−)annihilation data corresponding to an integrated luminosity of 2.93 fb^(−1)taken at the center-of-mass energy√s=3.773 GeV with the BESIII detector,a joint amplitude analysis is performed on the decays D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η).The fit fractions of individual components are obtained,and large interferences among the dominant components of the decays D^(0)→a_(1)(1260)π,D^(0)→π(1300)π,D^(0)→ρ(770)ρ(770),and D^(0)→2(ππ)_(S)are observed in both channels.With the obtained amplitude model,the CP-even fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are determined to be(75.2±1.1_(stat).±1.5_(syst.))%and(68.9±1.5_(stat).±2.4_(syst.))%,respectively.The branching fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are measured to be(0.688±0.010_(stat.)±0.010_(syst.))%and(0.951±0.025_(stat.)±0.021_(syst.))%,respectively.The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of D^(0)→4πwhen used to determine the CKM angleγ(ϕ_(3))via the B^(−)→DK^(−)decay.

Determination of the number ofψ(3686)events taken at BESⅢ

The number ofψ(3686)events collected by the BESⅢdetector during the 2021 run period is determined to be(2259.3±11.1)×10~6 by counting inclusiveψ(3686)hadronic events.The uncertainty is systematic and the statistical uncertainty is negligible.Meanwhile,the numbers ofψ(3686)events collected during the 2009 and 2012run periods are updated to be(107.7±0.6)×10~6 and(345.4±2.6)×10~6,respectively.Both numbers are consistent with the previous measurements within one standard deviation.The total number ofψ(3686)events in the three data samples is(2712.4±14.3)×10~6.

Measurement of integrated luminosity of data collected at 3.773 GeV by BESIII from 2021 to 2024

We present a measurement of the integrated luminosity of e^(+)e^(-)collision data collected by the BESIII detector at the BEPCII collider at a center-of-mass energy of Ecm=3.773 GeV.The integrated luminosities of the datasets taken from December 2021 to June 2022,from November 2022 to June 2023,and from October 2023 to February 2024 were determined to be 4.995±0.019 fb^(-1),8.157±0.031 fb^(-1),and 4.191±0.016 fb^(-1),respectively,by analyzing large angle Bhabha scattering events.The uncertainties are dominated by systematic effects,and the statistical uncertainties are negligible.Our results provide essential input for future analyses and precision measurements.

Measurements of the center-of-mass energies of e^(+)e^(-)collisions at BESIII

During the 2016-17 and 2018-19 running periods,the BESIII experiment collected 7.5 fb of e^(+)e^(-)collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV.These data samples are primarily used for the study of excited charmonium and charmoniumlike states.By analyzing the di-muon process e^(+)e^(-)→(γISR=FSR)μ^(+)μ^(-),we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV.Through a run-by-run study,we find that the center-of-mass energies were stable throughout most of the data-collection period.

Observation of e^+e^-→D_s^+■^((*)0)K^- and study of the P-wave D_s mesons

Studies of e^+e~→D_s^+■^((*)0)K^-and the P-wave charmed-strange mesons are performed based on an e^+e^-collision data sample corresponding to an integrated luminosity of 567 pb^(-1) collected with the BESIII detector at s^(1/2)=4.600 GeV. The processes of e^+e^-→D_s^+■^(*0)K^- and D_s^+■~0K^- are observed for the first time and are found to be dominated by the modes D_s^+D_(s1)(2536)^-and D_s^+D_(s2)~*(2573)^-, respectively. The Born cross sections are measured to be σ~B(e^+e^-→D_s^+■^(*0)K^-) =(10.1±2.3±0.8) pb and σ~B(e^+e^-→D_s^+■~0K^-) =(19.4±2.3± 1.6) pb, and the products of Born cross section and the decay branching fraction are measured to be σ~B(e^+e^-→D_s^+D_(s1)(2536)^-+c.c.)·B(D_(s1)(2536)^-→■^(*0)K^-)=(7.5±1.8±0.7) pb and σ~B(e^+e^-→D_s^+D_(s2)~*(2573)^-+ c.c.)·B(D_(s2)~*(2573)^-→■~0 K^-)=(19.7 ± 2.9 ±2.0) pb. For the D_(s1)(2536)^-and D_(s2)~*(2573)^-mesons, the masses and widths are measured to be M(D_(s1)(2536)^-)=(2537.7±0.5 ±3.1) MeV/c2, Γ(D_(s1)(2536)^-) =(1.7 ±1.2 ±0.6)MeV, and M(D_(s2)~*(2573)^-)=(2570.7±2.0 ±1.7) MeV/c^2, Γ(D_(s2)~*(2573)^-)=(17.2 ±3.6 ±1.1) MeV. The spin-parity of the D_(s2)~*(2573)^-meson is determined to be J^p= 2^+. In addition, the processes e^+e^-→D_s^+■^((*)0)K^-are searched for using the data samples taken at four(two) center-of-mass energies between 4.416(4.527) and 4.575 GeV, and upper limits at the 90% confidence level on the cross sections are determined.

Future Physics Programme of BESⅢ

There has recently been a dramatic renewal of interest in hadron spectroscopy and charm physics. This renaissance has been driven in part by the discovery of a plethora of charmonium-like XYZ states at BESⅢ and B factories, and the observation of an intriguing proton-antiproton threshold enhancement and the possibly related X(1835) meson state at BESⅢ, as well as the threshold measurements of charm mesons and charm baryons. We present a detailed survey of the important topics in tau-charm physics and hadron physics that can be further explored at BESⅢ during the remaining operation period of BEPCⅡ. This survey will help in the optimization of the data-taking plan over the coming years, and provides physics motivation for the possible upgrade of BEPCⅡ to higher luminosity.

Study of BESIII trigger efficiencies with the 2018 J/ψ data

Using a dedicated data sample taken in 2018 on the J/ψpeak,we perform a detailed study of the trigger efficiencies of the BESIII detector.The efficiencies are determined from three representative physics processes,namely Bhabha scattering,dimuon production and generic hadronic events with charged particles.The combined efficiency of all active triggers approaches 100%in most cases,with uncertainties small enough not to affect most physics analyses.

Number of J/ψ events at BESIII

Using inclusive decays of J/ψ aprecise determination of the number of J/ψ events collected with the BESIII detector was performed.For the two data sets taken in 2009 and 2012,the numbers of J/ψ events were recalculated to be(224.0±1.3)×10^(6) and(1088.5±4.4)×10^(6),respectively;these numbers are in good agreement with the previous measurements. For the J/ψ sample taken in 2017-2019,the number of events was determined to be(8774.0±39.4)×10^(6).The total number of J/ψ events collected with the BESIII detector was determined to be(10087±44)×10^(6),where the uncertainty is dominated by systematic effects,and the statistical uncertainty is negligible.

Evidence for the decays of ∧_c^+→∑^+η and ∑^+η’

We study the hadronic decays of ∧c+ to the final states ∑+η and ∑+η’,using an e+e-annihilation data sample of 567 pb-1 taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCⅡ collider.We find evidence for the decays ∧c+→∑+η and ∑+η’ with statistical significance of 2.5σ and 3.2σ,respectively.Normalizing to the reference decays ∧c+→∑+π0 and ∑+ω,we obtain the ratios of the branching fractions■and ■to be 0.35±0.16±0.02 and 0.86±0.34±0.04,respectively.The upper limits at the 90% confidence level are set to be■and■.Using BESIII measurements of the branching fractions of the reference decays,we determine B（∧c+→∑+η）=（0.41±0.19±0.05）%（<0.68%）and B（∧c+→∑+η’）=（1.34±0.53 ±0.19）%（<1.9%）.Here,the first uncertainties are statistical and the second systematic.The obtained branching fraction of ∧c+→∑+η is consistent with the previous measurement,and the branching fraction of ∧c+→∑+η’ is measured for the first time.

Observation of e^(+)e^(-)→pppñπ-+c.c.

Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESⅢdetector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 fb^(-1),the process e^(+)e^(-)→pppñπ+c.c.is observed for the first time with a statistical significance of 11.5σ.The average Born cross sections in the energy ranges of(4.160,4.380)GeV,(4.400,4.600)GeV and(4.610,4.700)GeV are measured to be(21.5±5.7±1.2)fb,(46.3±10.6±2.5)fb and(59.0±9.4±3.2)fb,respectively,where the first uncertainties are statistical and the second are systematic.The line shapes of the pñ and ppπ^(-)invariant mass spectra are consistent with phase space distributions,indicating that no hexaquark or di-baryon state is observed.

Search for hidden-charm tetraquark with strangeness in e^(+)e^(−)→K^(+)D_(s)^(∗−) D^(∗0 )+ c.c.

We report a search for a heavier partner of the recently observed Z_(cs)(3985)^(-) state,denoted as Z_(cs)^('-),in the process e^(+)e^(−)→K^(+)D_(s)^(∗−) D^(∗0 )+ c.c.,based on e^(*)e^(-)collision data collected at the center-of-mass energies of √s=4.661,4.682 and 4.699 GeV with the BESIII detector.The Z_(cs)^('-) is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark.A partial-reconstruction technique is used to isolate K^(+)recoil-mass spectra,which are probed for a potential contribution from Z_(cs)^('-)→D_(s)^(∗−) D^(∗0 )+ c.c.We find an excess of Z_(cs)^('-)→D_(s)^(*-)-D^(*0)(c.c.)candidates with a significance of 2.1o,after considering systematic uncertainties,at a mass of(4123.5±0.7_(sat)±4.7_(syst.))MeV/c^(2).As the data set is limited in size,the upper limits are evaluated at the 90%confidence level on the product of the Born cross sections(σ^(Borm))and the branching fraction(B)of Z_(cs)^('-)→D_(s)^(*-)-D^(*0),under different assumptions of the Z_(cs)^('-) mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies.The upper limits of σ^(Born).B are found to be at the level of O(1)pb at each energy.Larger data samples are needed to confirm the Z_(cs)^('-) state and clarify its nature in the coming years.

Measurement of e^+e^-→D■ cross sections at the ψ(3770) resonance

We report new measurements of the cross sections for the production of DD final states at theψ（3770）resonance.Our data sample consists of an integrated luminosity of 2.93 fb^（-1）of e~＋e^-annihilation data produced by the BEPCⅡ collider and collected and analyzed with the BESⅢ detector.We exclusively reconstruct three D^0and six D~＋hadronic decay modes and use the ratio of the yield of fully reconstructed DD events（“double tags”）to the yield of all reconstructed D or D mesons（“single tags”）to determine the number of D^0 D^0and D~＋D^-events,benefiting from the cancellation of many systematic uncertainties.Combining these yields with an independent determination of the integrated luminosity of the data sample,we find the cross sections to beσ（e~＋e^-→D^0D^0）=（3.615±0.010±0.038）nb andσ（e~＋e^-→D~＋D^-）=（2.830±0.011±0.026）nb,where the uncertainties are statistical and systematic,respectively.